As a method for casting an anode for the electrolysis of copper, the Walker method is widely adopted wherein a melted copper is poured into mold M arranged horizontally as shown in FIG. 1.
In the casting according to the Walker method, anode A, for the electrolysis of copper, as shown in FIG. 2 is formed by pouring a melted copper comprising a refined crude copper into concave S which is partitioned by upper surface 1a of base portion 1 and inner circumferential surface (or inner side surface) 2a of edge portion 2 protruded toward upward from the upper surface 1a of the base portion 1 of the mold M for the anode.
Heretofore, when horizontal castings is performed by using mold M having such a shape as shown in FIG. 1, specifically at the time when a mold release agent (or parting agent) is applied on the upper surface 1a of the base portion 1, a water soluble composition of a mold release agent prepared by dispersing a powder of a clay in water was used for the purpose of improving the life of a mold or the mold release effect of a cast product.
However, since water soluble compositions of a conventional mold release agent are inferior in heat resistance, when they were used as mold release agent for casting copper, for instance, such problems occurred that a gas is apt to generate on the flat portion of a cast anode for the electrolysis of copper, and unevenness (protuberance) due to the gas is formed and the casting surface of products is dirtily discolored to black to cause an inferior appearance.
As the composition of mold release agent, oil type mold release agents are also known. However, since the oil type mold release agents have a problem of the pollution of work environment and atmospheric air due to soot and fire, and have the problem that the casting surface is dirtily discolored to black, the oil type mold release agents are scarcely used in practice.